Image capturing apparatus

ABSTRACT

An image capturing apparatus can use a reading time from an image sensor efficiently. To achieve the object, the image capturing apparatus includes an image capturing unit which is configured to (i) capture image data (ii) separate the image data having a plurality of color components into a plurality of fields, and (iii) output each of the plurality of fields, the image-capturing unit being switchable between a first mode and a second mode, and a selecting unit which is configured to select two or more, but not all, of a plurality of fields, an image-generating unit which generates a low-resolution image based on image data of a field being selected by the selecting unit, and a controlling unit that is configured to cause the image-generating unit to generate the low-resolution image while the controlling unit outputs a field other than the field selected by the selecting unit.

CROSS REFERENCE TO THE RELATED APPLICATIONS

This is a Continuation of application Ser. No. 12/314,664 filed Dec. 15,2008, which in turn claims the benefit of priority from Japanese PatentApplication No. 2007-332281, filed on Dec. 25, 2007, the entire contentsof which are incorporated herein by reference. The disclosure of theprior applications are hereby incorporated by reference herein in itsentirety.

BACKGROUND

1. Field

The present application relates to an image capturing apparatus whichobtains an image by capturing an image of a subject.

2. Description of the Related Art

An electronic camera having an image sensor which separates a capturedimage of a subject into fields and reads the fields has beenpopularized. The applicant of the present invention has already proposedan electronic camera as an invention described in Japanese UnexaminedPatent Application Publication No. 2004-135225. The proposed electroniccamera can shorten the capturing interval by generating an image suitedto be displayed on a display device for checking a captured result(hereinafter referred to as “quick view image”) or an image suited forlist display (hereinafter referred to as “thumbnail image”) beforecompletion of reading of all the fields.

The number of fields to be read however has increased with the recentadvance of increase in the number of pixels used in the image sensor.For this reason, the time up to completion of reading of all the fieldshas become longer. As a result, the user's waiting time has becomelonger problematically.

SUMMARY

A proposition of the present embodiments is to use the reading time froman image sensor efficiently.

To achieve the proposition, the image capturing apparatus includes animage capturing unit which separates a color image of a subject beingcaptured by an image sensor having pixels of colors into three or morefields and outputs said three or more fields successively, and an imageprocessing unit which generates a low-resolution image which is lower inresolution than the color image obtained by the image capturing unit,based on output of one or more fields among said three or more fields,said one or more fields being able to extract color information of allthe colors, wherein the image processing unit starts generation of thelow-resolution image in a period in which fields other than said one ormore fields for generating the low-resolution image are read.

Incidentally, the low-resolution image is an image for checking a resultof capturing, and the image capturing apparatus may further include adisplay unit which displays the low-resolution image when thelow-resolution image is generated by the image processing unit.

The image capturing apparatus may further include a field selecting unitwhich selects one field from the fields, wherein the image processingunit includes a pre-processing part which performs pre-processing on thecolor image output from the image capturing unit and a post-processingpart which directly receives an output of the pre-processing part andperforms post-processing on the pre-processed color image, and when thelow-resolution image is to be generated, the color image of one fieldselected by the field selecting unit is directly transferred from thepre-processing part to the post-processing part to thereby perform thepre-processing and the post-processing integrally and sequentially.

The image processing unit may generate a first image lower in resolutionand a second image lower in resolution, and the field selecting unit mayselect one field for generating the first image and one field forgenerating the second image, respectively.

The image processing unit may include a pre-processing part whichperforms pre-processing on the color image output from the imagecapturing unit, a post-processing part which performs post-processing onthe pre-processed color image, and a pixel averaging part which directlyreceives an output of the post-processing part and averages any pixelsof the post-processed color image, and when the low-resolution image isto be generated, a first low-resolution image is generated by thepost-processing part and the generated first low-resolution image isdirectly transferred from the post-processing part to the pixelaveraging part to thereby generate a second low-resolution image whichis lower in resolution than the first low-resolution imagesimultaneously.

The image processing unit may include a white balance adjusting part,and when the low-resolution image is to be generated, the white balanceadjusting part performs white balance adjustment in accordance with awhite balance adjustment value decided in advance.

The image processing unit may include a pre-processing part whichperforms pre-processing on the color image output from the imagecapturing unit and a post-processing part which performs post-processingon the pre-processed color image, the image capturing apparatus mayfurther include a plurality of buffer memory areas which store the colorimage pre-processed by the pre-processing part and a high-speedcontinuous capturing mode which performs, as parallel processing, aprocess of performing the pre-processing on the color image of one frameoutput from the image capturing unit and storing the pre-processed colorimage in one of the buffer memory areas and a process of performing thepost-processing on the color image of a previous frame stored in anotherof the buffer memory areas, and the image processing unit does not startgeneration of the low-resolution image in a period of reading of fieldsother than said one or more fields for generating the low-resolutionimage while image capturing is executed in the high-speed continuouscapturing mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of an electroniccamera 1 according to an embodiment.

FIG. 2 is a view for explaining a Bayer arrangement.

FIG. 3 is a block diagram showing the details of an image processingpart 13.

FIG. 4 is a view for explaining a view operation.

FIG. 5 is a view for explaining a still image capturing operation.

FIG. 6 is a flow of image data during the view operation.

FIG. 7 is a diagram for explaining an image buffer of an SDRAM 19.

FIG. 8 is a view for explaining generation of a main image.

FIG. 9 is a flow of image data during the still image capturingoperation.

FIG. 10 is another diagram for explaining an image buffer of the SDRAM19.

FIG. 11 is another diagram for explaining an image buffer of the SDRAM19.

FIGS. 12A to 12D are timing charts showing still image capturingsequences respectively.

FIGS. 13A and 13B are timing charts of an image signal output of a CCD11 during the still image capturing operation.

FIGS. 14A and 14B are views for explaining generation of a quick viewimage.

FIG. 15 is a flow of data during generation of a quick view image.

FIG. 16 is a flow of data during generation of a thumbnail image.

FIG. 17 is another flow of data during generation of a quick view imageand a thumbnail image.

FIGS. 18A and 18B are other timing charts showing still image capturingsequences respectively.

FIG. 19 is another flow of data during generation of a quick view imageand a thumbnail image.

FIG. 20 is another flow of data during generation of a quick view imageand a thumbnail image.

FIG. 21 is another flow of data during generation of a quick view imageand a thumbnail image.

FIG. 22 is a view for explaining a high-speed continuous image capturingmode.

FIG. 23 is another diagram for explaining an image buffer of SDRAM 19.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings.

The configuration of an electronic camera 1 according to an embodimentwill be described first with reference to FIG. 1.

As shown in FIG. 1, the electronic camera 1 includes respective parts,i.e. an image-capturing lens 10, a CCD 11, an AFE (Analog Front End) 12,and an image processing part 13. The image-capturing lens 10 includes afocus lens, a zoom lens, a lens drive motor, etc. which are not shown.As shown in FIG. 2, the CCD 11 has a Bayer arrangement color filter.Incidentally, the CCD 11 is not limited to this example. The CCD 11 mayhave another filter arrangement such as a stripe arrangement or may bereplaced with another image sensor than the CDD. An image of a subjectcaptured by the CCD 11 through the image-capturing lens 10 istransformed into an image signal by the CCD 11. The image signal isoutput to the AFE 12. The output image signal is converted into digitaldata (hereinafter referred to as “image data”) by the AFE 12. The imagedata is output to the image processing part 13.

The electronic camera 1 further includes respective parts, i.e. a TG(Timing Generator) 14, an MDIC (Motor Driver IC) 15, an SIO (SerialInput/Output) 16, and a PIO (Parallel Input/Output) 17. The TG 14 drivesthe CCD 11 and the AFE 12 to perform exposure, image signal output, etc.The MDIC 15 drives the lens drive motor of the image-capturing lens 10.The SIO 16 controls the TG 14 and the MDIC 15. The PIO 17 controls theMDIC 15.

The electronic camera 1 further includes respective parts, i.e. a JPEGcompression part 18, an SDRAM 19, an SDRAM controller 20, an LCD 21, anda display controller 22. The JPEG compression part 18 compresses andexpands image data subjected to image processing by the image processingpart 13. The SDRAM 19 temporarily stores image data when the image datais subjected to image processing or image compression. The SDRAMcontroller 20 is an interface with the SDRAM 19. The LCD 21 displaysimage data and various kinds of information. The display controller 22controls the LCD 21. Incidentally, the respective parts, i.e. the imageprocessing part 13, the JPEG compression part 18, the SDRAM controller20 and the display controller 22 are coupled to one another by an imagebus.

The electronic camera 1 further includes respective parts, i.e. a memorycard 23, a card I/F part 24, a USB I/F part 25 and a clock generator 26,and a CPU 27. The memory card 23 is removable and used for recordingimage data, etc. The card I/F part 24 is an interface with the memorycard 23. The USB I/F part 25 can be coupled to a host PC, etc. The clockgenerator 26 supplies operating clocks to the respective parts. The CPU27 controls the respective parts. Incidentally, the respective parts,i.e. the image processing part 13, the SIO 16, the PIO 17, the jPEGcompression part 18, the SDRAM controller 20, the display controller 22,the card I/F part 24, the USB I/F part 25, the clock generator 26 andthe CPU 27 are coupled to one another by a CPU bus.

FIG. 3 is a block diagram showing the details of the image processingpart 13. As shown in FIG. 3, the image processing part 13 has apre-processing part 30, and a post-processing part 31. Thepre-processing part 30 has respective parts, i.e. a defect correctingpart 32, an OB clamp processing part 33, a sensitivity-ratio adjustingpart 34, a 3A-evaluated value calculating part 35, and an output buffer36. The defect correcting part 32 applies defect pixel correction toimage data input from the AFE 12. The OB clamp processing part 33decides the black level of the image data corrected by the defectcorrecting part 32. The sensitivity-ratio adjusting part 34 corrects thesignal levels of R, G and B by applying sensitivity ratio adjustment tothe image data processed by the OB clamp processing part 33. The3A-evaluated value calculating part 35 calculates respective evaluatedvalues of AWB (Auto White Balance) in addition to the aforementioned AEand AF based on the output of the sensitivity-ratio adjusting part 34.Calculation results of the 3A-evaluated value calculating part 35 areoutput to the CPU 27 through the CPU bus. The output of thesensitivity-ratio adjusting part 34 is output to the post-processingpart 31 and output to the image bus via the output buffer 36.

The post-processing part 31 has respective parts, i.e. a horizontaldecimation part 40, a WB adjusting part 41, a γ correcting part 42, acolor interpolating part 43, a color converting & color correcting part44, a resolution converting part 45, a spatial filtering part 46, a CbCrdecimation part 47, an input buffer 48, and an output buffer 49.

The horizontal decimation part 40 reduces the number of horizontalpixels by applying horizontal decimation to the image data pre-processedby the pre-processing part 30. The WB adjusting part 41 applies whitebalance adjustment to the image data decimated by the horizontaldecimation part 40, based on the AWB evaluated value, etc. calculated bythe 3A-evaluated value calculating part 35. They correcting part 42applies γ correction to the image data white-balance-adjusted by the WBadjusting part 41. The color interpolating part 43 generates image datahaving three colors per pixel from Bayer arrangement image data havingone color per pixel by applying color interpolation to the image datacorrected by the γ correcting part 42. The color converting & colorcorrecting part 44 generates image data in a target color space (e.g.sRGB) by applying color conversion and color correction to the imagedata interpolated by the color interpolating part 43. The image data isgenerally image data with YCbCr=4:4:4.

The resolution converting part 45 generates image data with a targetsize by applying a resolution conversion process to the image datacorrected by the color converting & color correcting part 44. Forexample, for a view operation which will be described later, image datawith a QVGA (320∴240) size or a VGA (640×480) size is generated. Thespatial filtering part 46 applies a spatial filtering process to theimage data converted by the resolution converting part 45. Specifically,the spatial filtering part 46 applies an edge emphasizing process to a Ysignal and applies a low-pass filtering process to color-differencesignals (a Cb signal and a Cr signal). The CbCr decimation part 47applies a decimation process to color-difference signals (a Cb signaland a Cr signal) to generate image data, for example, with YCbCr=4:2:2and output the image data to the output buffer 49. The output of theoutput buffer 49 is coupled to the image bus. While the output from theimage bus is coupled to the input buffer 48, the output of the inputbuffer 48 is coupled to the horizontal decimation part 40 and the colorconverting & color correcting part 44.

In the electronic camera 1 having the aforementioned configuration,there are a view operation and a still image capturing operation ascapturing operations. The view operation is an operation of generatingand displaying a through image to check a composition in real time. Thestill image capturing operation is an operation of generating an image(hereinafter referred to as “main image”) by main image capturing.

In the view operation, a high frame rate (e.g. 30 fps) is obtainedbecause a decimated image signal is output from the CCD 11 as shown inFIG. 4. The view operation is suited for real-time observation of asubject on the LCD 21, photometric measurement for AE (Auto Exposure) orexecution of AF (Auto Focusing).

On the other hand, in the still image capturing operation, an imagesignal with all pixels is output from the CCD 11 as shown in FIG. 5.Accordingly, the image signal is high in resolution and is output in thecondition that the image signal is separated into a plurality of fields.Although FIG. 5 shows an example where 4 fields are output, the numberof fields has a tendency toward increase with the advance of increase innumber of pixels used in the CCD 11.

In the aforementioned view operation, post-processing due to thepost-processing part 31 can be directly applied to the image datapre-processed by the pre-processing part 30 because adjacent lines of animage signal are output sequentially from the CCD 11 as shown in FIG. 4.That is, in the view operation, the pre-processing part 30 inputs thepre-processed image data to the post-processing part 31 directly. Then,the image data post-processed by the post-processing part 31 istemporarily stored in the SDRAM 19 via the image bus and the SDRAMcontroller 20. Further, the image data from the SDRAM 19 passes throughthe SDRAM controller 20, the image bus and the display controller 22successively and is displayed as a through image on the LCD 21.

On the other hand, in the aforementioned still image capturingoperation, an interpolating process or the like in the post-processingdue to the post-processing part 31 cannot be executed because the imagesignal is output from the CCD 11 in the condition that the image signalis separated into a plurality of fields as shown in FIG. 5. For example,in a first field shown in FIG. 5, a line n+4 is output next to a line n.Since lines n+1, n+2 and n+3 are inserted between the lines n and n+4, aprocess such as color interpolation, resolution conversion or spatialfiltering using adjacent lines of image data cannot be applied to imagedata of the first field. In the aforementioned still image capturingoperation, therefore, image data of the fields are pre-processed by thepre-processing part 30 respectively, temporarily stored in the SDRAM 19and combined into a frame image on the SDRAM 19 and then post-processedby the post-processing part 31.

FIG. 6 shows a flow of image data during the view operation. The CPU 27performs image processing along an arrow (1) and displays a throughimage along an arrow (2). Incidentally, in order to display the throughimage continuously, the two image buffers of a V1 buffer 60 and a V2buffer 61 as shown in FIG. 7 are prepared so that the two image buffersare switched alternately every frame. When a release button ishalf-pushed, the CPU 27 performs AE operation using an AE evaluatedvalue and AF using an AF evaluated value based on the 3A-evaluated valuecalculating part 35 in preparation for the still image capturingoperation. When the release button is full-pushed after it ishalf-pushed, the CPU 27 performs exposure for still image capturingbased on a result of the aforementioned AE operation after completion ofAF and goes to the still image capturing operation.

The exposure for still image capturing is terminated by the closure of amechanical shutter not shown, so that an image signal separated into aplurality of fields as shown in FIG. 5 is output from the CCD 11. Whileimage data of each field is pre-processed by the pre-processing part 30and then stored in the SDRAM 19, the CPU 27 calculates an AWB evaluatedvalue in the 3A-evaluated value calculating part 35 in accordance witheach field. When all the pre-processed image data of the fields arestored in the SDRAM 19, the CPU 27 sets a WB adjustment value obtainedfrom the aforementioned AWB evaluated values in the WB adjusting part41. Then, the CPU 27 reads image data stored in the SDRAM 19 in(progressive) order of lines so that the image data is post-processed bythe post-processing part 31.

Incidentally, the three images of a quick view image for checkingcapturing, a thumbnail image suited for list display and a main imageare generated in the still picture capturing. These images are generatedby post-processing the pre-processed image data respectively. The sizeof the main image is so large that the main image cannot be usuallygenerated by one post-process. Therefore, as shown in FIG. 8, the mainimage is generated in such a manner that pre-processed image data isseparated into narrow strip blocks, each of the blocks ispost-processed, and the post-processed blocks are combined. However, thesize of each post-processed block is reduced because surrounding pixelsare cut off. Therefore, as shown in FIG. 8, boundary portions ofadjacent blocks are made to overlap with each other so thatpost-processed images are combined correctly. Incidentally, when themain image is to be generated, the horizontal decimation part 40 isgenerally bypassed so that full-resolution pixels are fed to thepost-stage. On the other hand, the size of each of the quick view imageand the thumbnail image is small so that each of the quick view imageand the thumbnail image can be generated by one post-process (withoutseparation into strip blocks as described with reference to FIG. 8) ifit has been initially subjected to horizontal decimation.

A still picture capturing operation according to the related art will bedescribed first for the sake of comparison. FIG. 9 shows a flow of imagedata during the still image capturing operation. The CPU 27 performspre-processing along an arrow (1) and performs post-processing alongarrows (2) and (3). Each of the pre-processing part 30 and thepost-processing part 31 has one image processing pipeline. Accordingly,each of the quick view image, the thumbnail image and the main image isgenerated sequentially. Each of the three images is stored in the SDRAM19. Incidentally, it is preferable that the quick view image isgenerated first so that the user can check the contents of the capturedmain image quickly. It is preferable that the thumbnail image is thengenerated and the main image is finally generated. This is because ageneral file format standard called Exif/DCF uses data arrangement thatthe thumbnail image is recorded on a header portion of a JPEG file andthe main image is recorded on a tail portion of the JPEG file. The CPU27 displays image data of the quick view image on the LCD 21 along anarrow (6).

The CPU 27 further records the thumbnail image and the main image bothin a JPEG compressed format. The CPU 27 performs JPEG compression alongarrows (4) and (5). Because one part is provided as the JPEG compressionpart 18, compression of the thumbnail image and compression of the mainimage are performed sequentially. In this case, it is preferable thatthe thumbnail image and the main image are compressed in this order. TheCPU 27 combines compressed data of the thumbnail image and compresseddata of the main image into one file on the SDRAM 19 in accordance withthe Exif/DCF format and records the file on the memory card 23 throughthe card I/F part 24 along an arrow (7).

As described above, a plurality of data flows appear during the stillimage capturing operation. Therefore, a plurality of image buffers areprepared in the SDRAM 19 correspondingly to the data flows. As shown inFIG. 10, the SDRAM 19 has respective image buffers, i.e. an R buffer 62,a T buffer 63, an M buffer 64, a T-J buffer 65, an M-J buffer 66, and aQ buffer 67.

As shown in FIG. 10, the CPU 27 stores pre-processed image data in the Rbuffer 62. The image data stored in the R buffer 62 is post-processed sothat image data of the thumbnail image thus generated is stored in the Tbuffer 63. The image data stored in the R buffer 62 is post-processed sothat image data of the main image thus generated is stored in the Mbuffer 64. The image data stored in the T buffer 63 is JPEG-compressedby the JPEG compression part 18 so that image data of the compressedimage thus generated is stored in the T-J buffer 65. The image datastored in the M buffer 64 is JPEG-compressed by the JPEG compressionpart 18 so that image data of the compressed image thus generated isstored in the M-J buffer 66. The image data stored in the T-J buffer 65and the image data stored in the M-J buffer 66 are combined into onefile on one SDRAM 19 as described above, so that the file is recorded onthe memory card 23. In addition, the image data stored in the R buffer62 is post-processed so that image data of the quick view image thusgenerated is stored in the Q buffer 67. The image data stored in the Qbuffer 67 is displayed on the LCD 21 through the display controller 22as described above.

Although the data flow reaching the R buffer 62 is drawn as one line inFIG. 10, a plurality of data flows as shown in FIG. 11 are actuallyprovided because image data separated into fields as shown in FIG. 5 areinput to the R buffer 62 successively. As shown in FIG. 11, the SDRAM 19has respective image buffers, i.e. an R1 buffer 68, an R2 buffer 69, anR3 buffer 70 and an R4 buffer 71 in place of the R buffer 62 shown inFIG. 10. These image buffers may be configured so that the R buffers (R1to R4) 62 of respective fields have discrete addresses so that aone-frame image can be read in (progressive) order of lines regardlessof the number of original fields. Image data of the fourth field isinput to the R4 buffer. The CPU 27 starts post-processing due to thepost-processing part 31 after all image data of the four fields arestored in the image buffers respectively.

FIG. 12A is a timing chart showing a sequence for capturing a stillimage as described above. In FIG. 12A, “Q image”, “T image” and “Mimage” express a quick view image, a thumbnail image and a main imagerespectively. As shown in FIG. 12A, outputting of an image signal fromthe CCD 11 and pre-processing due to the pre-processing part 30 areperformed in parallel so that image data of fields subjected topre-processing are stored in the R buffers (the R1 buffer 68 to the R4buffer 71) successively. When image data of all the fields are stored inthe R buffers, post-processing due to the post-processing part 31 isapplied to the image data to generate the three images of a quick viewimage, a thumbnail image and a main image successively. Incidentally,the CPU 27 displays the quick view image on the LCD 21 immediately afterthe CPU 27 generates the quick view image. Then, the CPU 27 applies JPEGcompression due to the JPEG compression part 18 to the thumbnail imageand the main image successively. Finally, the CPU 27 records compresseddata of the thumbnail image and compressed data of the main image on thememory card 23 successively.

Incidentally, the thumbnail image and the main image are generatedsuccessively and JPEG-compressed successively. Therefore, when thethumbnail image is JPEG-compressed during generation of the main image,and compressed data of the thumbnail image is recorded during JPEGcompression of the main image as shown in FIG. 12B, a plurality ofprocesses can be executed while overlapping with one another so that thetotal processing time (capturing time) can be shortened. Further, whenodd fields are read from the CCD 11, a low-resolution color image suchas a quick view image or a thumbnail image can be generated from imagedata of only one field in parallel with outputting of an image signalfrom the CCD 11 as described above in the Related Art (see FIG. 12C).

FIG. 12D is a timing chart showing a high-speed still image capturingsequence obtained by combination of FIG. 12B and FIG. 12C. As shown inFIG. 12D, generation of a quick view image from image data of only onefield is performed in parallel with outputting of an image signal fromthe CCD 11. Further, JPEG compression of a thumbnail image is started inthe middle of generation of a main image. As a result, there is a largemerit that the quick view image and the thumbnail image can be generatedearlier.

Further, an example in which generation of only a quick view image isperformed in parallel with outputting of an image signal from the CCD 11is shown in FIGS. 12C and 12D. However, if the CCD 11 is of a 3-fieldoutput type, an image signal of the three fields is output successivelyin synchronization with a vertical synchronizing signal (VD signal) fromthe TG 14 as shown in FIG. 13A. Accordingly, when a quick view image isgenerated during reading of the first or second field and a thumbnailimage is generated during reading of the second or third field, thegeneration of the quick view image and the thumbnail image can becompleted before the outputting of the image signal of all the fieldsfrom the CCD 11 is completed.

Incidentally, as described above, the time required for completion ofreading of all the fields from the CCD has become longer with theadvance of increase in number of fields to be read. Therefore, in thisinvention, generation of the quick view image and the thumbnail image isstarted earlier in order to use the reading time efficiently.

FIGS. 14A and 14B are views for explaining generation of a quick viewimage in this embodiment. FIG. 14A shows an example where the CCD 11 isof a 3-field output type. FIG. 14B shows an example where the CCD 11 isof a 4-field output type. When the CCD 11 is of a 3-field output type,one field contains all color signal components (R, G and B) as shown inFIG. 14A. Accordingly, a quick view image and a thumbnail image can begenerated from image data of only one field (the first field in theexample shown in FIG. 14A). On the other hand, when the CCD 11 is of a4-field output type, each field lacks one color signal component asshown in FIG. 14B. For example, the first field does not contain any Bsignal, and the second field does not contain any R signal. Therefore,in such a case, a quick view image and a thumbnail image are generatedfrom image data of two fields (the first and second fields in theexample shown in FIG. 14B) from which all color information can beextracted. Although all color information can be extracted from theimage signal of two fields in the example shown in FIG. 14B, a smallestnumber of fields allowed to extract all color information may beproperly used for a CCD etc. using color filters containing three ormore color components.

For example, as shown in FIG. 13B, when the CCD 11 is of a 4-fieldoutput type, a quick view image and a thumbnail image can be generatedfrom image data of the first and second fields without waiting forcompletion of outputting of an image signal of all the fields from theCCD 11, at the point of time of completion of outputting of an imagesignal of the second field. Accordingly, the period of reading of thethird and fourth fields can be used efficiently.

On this occasion, it is preferable that generation of the quick viewimage has priority over generation of the thumbnail image. This isbecause the user can check capturing based on the quick view imageearlier while the quick view image can be used for generating thethumbnail image. In comparison between an image obtained by combiningthe first and second fields and a quick view image generated from theimage, the size (resolution) of the quick view image is generallysmaller (lower). Accordingly, when the quick view image is generatedfirst and used for generating the thumbnail image, processing can beaccelerated.

FIG. 15 shows a flow of data during generation of a quick view image. Asshown in FIG. 15, the CPU 27 reads image data of the first and secondfields stored in the SDRAM 19 (the R1 buffer 68 and the R2 buffer 69)while storing image data of the third and fourth fields in the SDRAM 19(the R3 buffer 70 and the R4 buffer 71). Then, the read image data ofthe first and second fields are post-processed by the post-processingpart 31 to generate a quick view image.

FIG. 16 shows a flow of data during generation of a thumbnail image fromthe quick view image generated by the data flow of FIG. 15. As shown inFIG. 16, the CPU 27 reads image data of the quick view image stored inthe SDRAM 19 (the Q buffer 67) and applies a reduction process, etc. dueto the resolution converting part 45 of the post-processing part 31 tothe read image data of the quick view image to thereby generate athumbnail image.

As described above with reference to FIGS. 15 and 16, even when thequick view image and the thumbnail image are generated sequentially, thetotal processing time can be shortened. When, for example, the totalreading time of the third and fourth fields is required for generatingthe quick view image, the whole processing is performed in the sametiming as in FIG. 12C or 12D. When the quick view image is generated ina shorter time, the total processing time can be further shortenedbecause generation of the thumbnail image can be executed ahead ofschedule. For example, this can be achieved when the frequency ofprocessing clocks concerned with the post-processing part 31 is set at ahigh frequency. When generation of the quick view image is completed atan early timing of the reading period of the fourth field, generation ofthe thumbnail image can be completed before an end of the reading periodof the fourth field. In this case, generation of the thumbnail imagefrom the quick view image as described above with reference to FIG. 16is effective.

On the other hand, as described above with reference to FIG. 13A, whenthe CCD 11 is of a 3-field output type, a quick view image and athumbnail image can be generated from image data of only the firstfield. Accordingly, the reading period of the second and third fieldscan be used efficiently. In this case, as described above with referenceto FIG. 15, the CPU 27 reads image data of the first field stored in theSDRAM 19 (the R1 buffer 68) and applies post-processing due to thepost-processing part 31 to the read image data of the first field togenerate a quick view image and a thumbnail image.

As described above with reference to FIG. 14A, when one filed containsall color signal components (R, G and B), generation of a quick viewimage and a thumbnail image by a data flow shown in FIG. 17 can makeprocessing more efficient. That is, as shown in FIG. 17, the CPU 27transfers image data of one field pre-processed by the pre-processingpart 30 from the pre-processing part 30 to the post-processing part 31directly. Then, the image data is post-processed by the post-processingpart 31 to generate a quick view image. The quick view image is storedin the SDRAM 19 (the Q buffer 67).

The same processing as in the data flow during the view operation shownin FIGS. 6 and 7 can be made to transfer image data from thepre-processing part 30 to the post-processing part 31 directly. Aplurality of quick view images are however generated when image data issimply transferred from the pre-processing part 30 to thepost-processing part 31 directly. A field selecting unit for selectingone of the fields is therefore provided so that image data of only onefield set by the field selecting unit in advance can be directlytransferred to the post-processing part 31 to thereby generate one quickview image. According to this configuration, the image processing part13 performs control automatically (without necessity of the CPU 27'scontrolling the operation/suspension of the post-processing part 31) tooperate the post-processing part 31 in the reading period of only oneselected field but suspend the post-processing part 31 in the readingperiod of the other fields.

Because a reduction process is generally performed when a quick viewimage is generated, the horizontal decimation part 40 can be usedefficiently in the same manner as in the view operation described abovewith reference to FIGS. 6 and 7. On the other hand, image data of allthe fields pre-processed by the pre-processing part 30 must be stored inthe SDRAM 19 so that a high-resolution main image can be generatedafterward. As shown in FIG. 17, there are hence provided two data flowscorresponding to the quick view image output from the post-processingpart 31 and the image data output from the pre-processing part 30.

According to the configuration described with reference to FIG. 17, itis possible to expect a merit of generating the quick view image in realtime and a merit of reducing data traffic on the SDRAM 19. For example,if generation of the quick view image is completed in the reading periodof the first field in FIG. 13A, two reading periods of the second andthird fields are free sufficiently to generate the thumbnail image. Inthis case, the thumbnail image can be generated from the quick viewimage as described above with reference to FIG. 16. When the thumbnailimage is generated from the quick view image, completion of generationof the thumbnail image in the reading period of the second field can beachieved. That is, the processing time can be shortened as shown in atiming chart of FIG. 18A. When the processing clock is further adjustedappropriately, processing such as starting or terminating compression ofthe thumbnail image in the reading period of the third field can beperformed further ahead of schedule.

Instead of generation of the thumbnail image from the quick view imageas described above with reference to FIG. 16, there may be used a methodin which the quick view image is generated from the image data of thefirst field in the reading period of the first field and the thumbnailimage is then generated from the image data of the second field in thereading period of the second field. In this case, the field used forgenerating the quick view image and the field used for generating thethumbnail image can be set respectively by the aforementioned selectionunit. According to this configuration, the processing time can beshortened at the same level as that in the case where the thumbnailimage is generated from the quick view image.

Alternatively, configuration may be made so that the quick view imageand the thumbnail image are generated simultaneously in parallel. Inmost cases, the size of the quick view image is a QVGA (320×240) size ora VGA (640×480) size. On the other hand, the size of the thumbnail imageis defined as a standard (160×120) size in the Exif/DCF format. It isfound from size comparison between the quick view image and thethumbnail image that the standard thumbnail image (160×120) in theExif/DCF format can be generated if the size of the quick view image isreduced to “1/N” times (in which N is an integer). It is a matter ofcourse that this good compatibility is effective in the case where thethumbnail image is generated from the quick view image as describedabove with reference to FIG. 16. On the other hand, the size reductionprocess is equivalent to a process of calculating an average of pixelvalues in a block “N pixels” (horizontal) by “N pixels” (vertical).Therefore, a bit shift technique which is a known technique can be usedfor generating the quick view image and the thumbnail imagesimultaneously in parallel. Specifically, 2 bits are shifted to theright for “¼” times (N=4) and 1 bit is shifted to the right for “½”times (N=2). Because such a circuit for calculating an average of pixelshas a very simple structure, increase in cost and power consumptioncaused by the provision of this circuit is allowable.

Therefore, as shown in a data flow of FIG. 19, a pixel averaging part 50is provided in the rear of the post-processing part 31. Post-processedimage data is input from the post-processing part 31 to the pixelaveraging part 50 directly. FIG. 19 shows an example where the CCD 11 isof a 4-field output type. When the quick view image has been generatedin the post-processing part 31, the pixel averaging part 50 calculatesan average of pixel values in a block 4 pixels (horizontal) by 4 pixels(vertical) (16 pixels in total) in the quick view image (i.e. increasesan integrated value of 16 pixels by 1/16 times (4-bit shift)) orcalculates an average of pixel values in a block 2 pixels (horizontal)by 2 pixels (vertical) in the quick view image (4 pixels in total) (i.e.increase an integrated value of 4 pixels by ¼ times (2-bit shift)).Then, the pixel averaging part 50 outputs the average as the value ofone pixel of the thumbnail image.

Then, the CPU 27 stores image data of the quick view image generated bythe post-processing part 31 in the SDRAM 19 (the Q buffer 67) and storesimage data of the thumbnail image generated by the pixel averaging part50 in the SDRAM 19 (the T buffer 63). That is, the processing time canbe shortened as shown in a timing chart of FIG. 18B.

Although the averaging process executed by the pixel averaging part 50is effective for generating the quick view image from image data of onefield, the averaging process is particularly effective for generatingthe quick view image from image data of two or more fields. The start ofgeneration of the quick view image from image data of two or more fieldsis always delayed compared with the start of generation of the quickview image from image data of one field. The delay can be howevercompensated when the quick view image and the thumbnail image aregenerated simultaneously as described above. For example, when the CCD11 is of a 4-field output type, generation of the quick view image canbe started at the point of time of completion of outputting of the imagesignal of the second field and generation of the thumbnail image can bestarted at the same time as described above with reference to FIG. 13B.Accordingly, both the quick view image and the thumbnail image can begenerated before the reading period of all the fields is terminated.

To further improve the processing speed for generating the quick viewimage from image data of two or more fields, image data reduced for thequick view image in advance (i.e. low-resolution RAW data) may be storedin the SDRAM 19. That is, as shown in a data flow of FIG. 20, whileimage data of all fields pre-processed by the pre-processing part 30 arestored in the SDRAM 19 (the R1 buffer 68 to the R4 buffer 71), imagedata of fields used for generating the quick view image are transferredfrom the pre-processing part 30 to the post-processing part 31 directly,size-reduced by the post-processing part 31 and stored in the SDRAM 19(a Q-R1 buffer 82 and a Q-R2 buffer 83). In this case, a reduction ratiofor the size reduction process in the horizontal decimation part 40 inthe post-processing part 31 is set so that an image slightly larger thanthe quick view image can be obtained.

Then, the horizontally size-reduced image data of the first and secondfields are stored in the SDRAM 19 (the Q-R1 buffer 82 and the Q-R2buffer 83) via the output buffer 49. Therefore, configuration is made sothat the output of the horizontal decimation part 40 can be connected tothe output buffer 49. Although the horizontal size reduction permits thequick view image to be generated at a high speed, combination of thehorizontal size reduction and vertical size reduction permits the quickview image to be generated at a higher speed when the total number offirst and second field lines is considerably larger than the number oflines in the quick view image (e.g. when the total number of first andsecond field lines is larger than twice as large as the number of linesin the quick view image).

The data stored in the Q-R1 and Q-R2 buffers 82 and 83 in FIG. 20 areBayer arrangement image data. The color arrangement in one field ishowever common to all the lines as described above with reference toFIG. 14B. Accordingly, even when, for example, the lines added up inFIG. 14B are first field lines n and n+4 or second field lines n+1 andn+5, the color arrangement is unchanged. That is, this is the same asthe case where two lines are added up as described in the view operationin FIG. 4. Accordingly, the aforementioned vertical size reduction canbe achieved by use of line averaging (addition and division). A linememory is however required when the line averaging is performed by bothaddition and division. That is, image data of one line horizontallysize-reduced by the horizontal decimation part 40 is stored in the linememory so that vertical size reduction can be performed by calculationof an average (addition and division due to bit shift) of the image dataand image data of the next line horizontally size-reduced in the samemanner as described above.

Generally, the time required for image processing is proportional to thesize of an image which is a subject of image processing. Therefore, theprocessing time can be shortened when the quick view image is generatedfrom the low-resolution RAW data (reduced Bayer arrangement image data)as described above with reference to FIG. 20. Incidentally, if it isdifficult to provide the aforementioned line memory, the quick viewimage can be generated at a high speed because even horizontal sizereduction executed by the horizontal decimation part 40 can dispensewith the separation of image data into strip blocks as shown in FIG. 8in addition to reduction in number of horizontal pixels.

A data flow shown in FIG. 21 which is a modification of FIG. 20 iseffective likewise. That is, as shown in FIG. 21, a quick view image isgenerated first and then a thumbnail image is generated from the quickview image. In this case, the processing time becomes longer than thatin the data flow shown in FIG. 20. Elongation of the processing time canbe however suppressed because the thumbnail image is generated from thequick view image. In addition, increase of hardware can be suppressedbecause it is unnecessary to provide any new structure such as a pixelaveraging circuit.

Alternatively, the following measures may be taken in consideration ofaccuracy in white balance adjustment executed by the WB adjusting part41 of the post-processing part 31. As described above with reference toFIG. 3, it is necessary to set an appropriate WB adjustment value in theWB adjusting part 41 when image data is post-processed by thepost-processing part 31. White balance adjustment is an adjustingprocess for reproducing an appropriate color by correcting change of thecolor temperature of illuminating light on a subject when the colortemperature changes. For the white balance adjustment, the CPU 27 setsthe WB adjusting part 41 at the WB adjustment value obtained from theAWB evaluated value calculated by the 3A-evaluated value calculatingpart 35 as described above with reference to FIG. 3. In the viewoperation in which a through image is displayed on the LCD 21, the AWBevaluated value is updated at a constant rate (e.g. at a rate of 30 fps)in accordance with new image data which is continuously input to thepre-processing part 30. Generally, it is unnecessary to change the WBadjustment value frequently because the color temperature ofilluminating light does not change rapidly. Accordingly, in the viewoperation, the WB adjustment value can be updated at a moderate rate.

On the other hand, in the still image capturing operation in which astill image is generated, the WB adjustment value is obtained based onthe AWB evaluated value generally extracted from image data per se ofthe still image because the still image is an independent image of oneframe. However, if the WB adjustment value is obtained based on the AWBevaluated value extracted from image data per se of a quick view imageor a thumbnail image to be generated, generation of the quick view imageor the thumbnail image is delayed. It is therefore preferable that theWB adjustment value used for generating the quick view image or thethumbnail image is decided in advance. For example, the WB adjustmentvalue may be the latest WB adjustment value used in the view operationjust before or may be obtained, as a WB adjustment value correspondingto the color temperature of illuminating light, from a database in theelectronic camera 1 if the color temperature of illuminating light canbe found in advance (e.g. as in flash photography). Then, the CPU 27performs white balance adjustment due to the WB adjusting part 41 inaccordance with the WB adjustment value decided in advance.

However, if the WB adjustment value can be calculated based on the AWBevaluated value at a high speed, the WB adjustment value may be obtainedbased on the AWB evaluated value extracted from image data per se of thequick view image or the thumbnail image to be generated. For example,when the CCD 11 is of a 3-field output type as described above withreference to FIG. 13A, an AWB evaluated value is extracted from imagedata of the first field in the reading period of the first field, a WBadjustment value is calculated based on the AWB evaluated valueextracted in the reading period of the first field, in the readingperiod of the second field, and a quick view image is finally generatedin the reading period of the third field. Because it is conceived thatthere is a high correlation between the respective fields, there is nolarge problem when the quick view image is generated from image data ofthe third field based on the AWB evaluated value extracted in thereading period of the first field.

On the other hand, for example, when the CCD 11 is of a 4-field outputtype as described above with reference to FIG. 13B, an AWB evaluatedvalue is extracted from image data of the first and second fields in thereading period of the first and second fields, a WB adjustment value iscalculated based on the AWB evaluated value extracted in the readingperiod of the first and second fields, in the reading period of thethird field, and a quick view image and a thumbnail image are generatedin the reading period of the fourth field. Incidentally, when a longtime is required for calculating the WB adjustment value, the WBadjustment value may be calculated in the reading period of the thirdand fourth fields so that the quick view image and the thumbnail imagecan be generated simultaneously after final reading of the fourth fieldis completed. Although the quick view image and the thumbnail imagecannot be generated in the period of reading of an image signal from theCCD 11, the total processing time can be shortened because the WBadjustment value can be calculated ahead of schedule. In this case,processing may be made in accordance with the data flow described withreference to FIG. 20.

Exceptional processing will be described below when the electroniccamera 1 has a high-speed continuous capturing mode. As shown in FIG.22, the high-speed continuous capturing mode is a capturing mode wherecapturing of one frame of the latest still image is made in parallelwith image processing (post-processing) of a previous frame, in parallelwith JPEG compression of a further previous frame and in parallel withrecording of a further previous frame. In the high-speed continuouscapturing mode, the three images of a quick view image, a thumbnailimage and a main image are generated in image processing(post-processing), the thumbnail image and the main image are compressedin JPEG compression processing, and compressed data of the thumbnailimage and the main image are recorded in recording processing. That is,in each step, images are processed in parallel.

It is necessary to provide a plurality of image buffers so that the foursteps shown in FIG. 22 can overlap with one another. For example, asshown in FIG. 23, an R1 buffer 68 and an R2 buffer 69 are provided inplace of the R buffer 62 shown in FIG. 10, and a Q1 buffer 72 and a Q2buffer 73 are provided in place of the Q buffer 67 shown in FIG. 10.Moreover, a T1 buffer 74 and a T2 buffer 75 are provided in place of theT buffer 63 shown in FIG. 10, and an M1 buffer 76 and an M2 buffer 77are provided in place of the M buffer 64 shown in FIG. 10. In addition,a T-J1 buffer 78 and a T-J2 buffer 79 are provided in place of the T-Jbuffer 65 shown in FIG. 10, and an M-J1 buffer 80 and an M-J2 buffer 81are provided in place of the M-J buffer 66 shown in FIG. 10. That is, asshown in FIG. 23, all the image buffers are doubled. With theconfiguration of the SDRAM 19, the four steps described with referenceto FIG. 22 can overlap with one other perfectly. Incidentally, each stepincludes smaller sub-steps which are executed sequentially.

In execution of image capturing in the high-speed continuous capturingmode described above, outputting of an image signal corresponding to oneframe of the latest still image from the CCD 11 is performed in parallelwith image processing (post-processing) of a previous frame performed bythe post-processing part 31. Accordingly, a quick view image or athumbnail image corresponding to one frame of the latest still imagecannot be generated in parallel with the outputting of the image signalfrom the CCD 11. Therefore, in execution of image capturing in thehigh-speed continuous capturing mode, generation of the quick view imageand the thumbnail image is not started during outputting of the imagesignal from the CCD 11. The quick view image and the thumbnail image aregenerated collectively and subsequently. In this case, the processingtime of each step becomes longer than that in image capturing in asingle capturing mode but the total processing time can be shortenedbecause new frames are captured successively. When it is difficult toprovided doubled image buffers as shown in FIG. 23 in terms of memorycapacity, etc., at least the R buffer may be doubled (as an R1 buffer 68and an R2 buffer 69) so that image capturing of the next frame can becontinued.

An example of combination of the aforementioned processes will bedescribed finally. When the CCD 11 is configured so that the readingmode can be switched in accordance with whether one field contains allcolor signal components (R, G and B) or not, processing modescorresponding to the respective cases may be provided so that one of theprocessing modes selected in accordance with switching of the readingmode can be executed. That is, configuration may be made so that a quickview image and a thumbnail image are generated from image data of onefield when one field contains all color signal components (R, G and B),whereas a quick view image and a thumbnail image are generated fromimage data of two or more fields when one field does not contain allcolor image components (R, G and B). With this configuration, optimumprocessing can be performed regardless of the configuration of the CCD11, the number of fields to be read and the switching of the readingmode.

As described above, according to this embodiment, generation of alow-resolution image is started in the reading period of remainingone(s) of all fields except part of the fields. Accordingly, the readingtime from the image sensor can be used efficiently.

Moreover, according to this embodiment, a display unit is furtherprovided for displaying an image for checking a result of capturing as alower-resolution image when the image is generated. Accordingly, thewaiting time of the user can be shortened.

Moreover, according to this embodiment, a field selecting unit forselecting one of fields is further provided so that a color image of onefield selected by the field selecting unit to generate a low-resolutionimage is transferred from the pre-processing part to the post-processingpart directly to thereby unify pre-processing and post-processing.Accordingly, the low-resolution image can be generated efficiently andquickly.

Moreover, according to this embodiment, a first low-resolution image anda second low-resolution image are generated in such a manner that thefield selecting unit selects either of a field used for generating thefirst image and a field used for generating the second image.Accordingly, low-resolution images can be generated sequentially andquickly without necessity of adding any special configuration.

Moreover, according to this embodiment, for generation of low-resolutionimages, a first image with a low resolution is generated by thepost-processing part and directly transferred from the post-processingpart to the image averaging part to thereby simultaneously generate asecond image with a lower resolution than that of the first image.Accordingly, low-resolution images can be generated efficiently andquickly.

Moreover, according to this embodiment, for generation of thelow-resolution images, the white balance adjusting part performs whitebalance adjustment in accordance with a white balance adjustment valuedecided in advance. Accordingly, low-resolution images can be generatedquickly while white balance adjustment can be performed appropriately.

Moreover, according to this embodiment, a high-speed continuouscapturing mode is provided so that generation of any low-resolutionimage is not started in the reading period of the remaining fieldsduring execution of image capturing in the high-speed continuouscapturing mode. Accordingly, the reading time from the image sensor canbe used efficiently regardless of the image capturing mode.

Although the respective sub-steps are drawn in the timing charts ofFIGS. 12A to 12D and FIGS. 18A and 18B so as to have equalized lengthsfor the sake of simplification in the aforementioned embodiment, thelengths of the respective sub-steps have no correlation with actualprocessing lengths. Generally, the processing time required forprocessing such as image processing, JPEG compression processing, datarecording, etc. is proportional to the amount of data used for theprocessing. That is, the longest processing time is required forgeneration and JPEG compression processing of the main image comparedwith generation of the quick view image and the thumbnail image. Withrespect to JPEG compression, the longest time is required forcompression of the main image. Accordingly, the three sub-steps of imageprocessing (post-processing), JPEG compression processing and datarecording are dedicated to processing of the main image so thatreduction of the image capturing time can be achieved. As describedabove in this embodiment, generation of the quick view image and thethumbnail image can be quickened to thereby achieve reduction of theimage capturing time.

When the quick view image which was heretofore used only for checkingimage capturing is JPEG-compressed and recorded on the memory card 23while associated with the main image, the quick view image can bedisplayed on the LCD 21 at the time of reproduction of the main image.As a result, in comparison with the case where the main image washeretofore size-reduced before displayed on the LCD 21, the waiting timeof the user can be shortened in this case. In this case, JPEGcompression processing may be applied to the quick view image as well asthe main image. A private area (maker note area) of Exif/DCF can be usedfor recording the quick view image.

In JPEG compression processing, bit rate control has been heretoforemade to keep the size of data of one frame almost constant. The bit ratecontrol can keep the number of image capturing frames constant inaccordance with the recording capacity of the memory card 23. There ishowever some case where JPEG compression must be repeated several timesunder the bit rate control, so that the image capturing time may becomeremarkably long. It is therefore desired that the amount of data isbrought close to a target value while the number of times in repetitionof compression is reduced as sufficiently as possible. On this occasion,the number of times in repetition of compression can be reduced when aquantization table for JPEG compression of the main image is decidedwith reference to information concerned with JPEG compression of thequick view image or the thumbnail image generated before the main image.

In each of the above-described embodiments, in the case of using animage signal having minimum number of fields (for example, 2 fields inthe embodiment) which can extract color information of all the colors inthe CCD to generate low-resolution images such as quick view images.However, the present invention is not limited to such an example. Thenumber of the fields of the image signal which is used for generatinglow-resolution images may be any numbers as long as the number of thefields of the image signal is more than the number of the minimum fieldsbut less than the number of all fields of the CCD.

The many features and advantages of the embodiments are apparent fromthe detailed specification and, thus, it is intended by the appendedclaims to cover all such features and advantages of the embodiments thatfall within the true spirit and scope thereof. Further, since numerousmodifications and changes will readily occur to those skilled in theart, it is not desired to limit the inventive embodiments to the exactconstruction and operation illustrated and described, and accordinglyall suitable modifications and equivalents may be resorted to, fallingwithin the scope thereof.

What is claimed is:
 1. An image capturing apparatus comprising: animage-capturing unit that is configured to (i) capture image data, (ii)separate the image data having a plurality of color components into aplurality of fields, and (iii) output each of the plurality of fields,the image-capturing unit being switchable between a first mode and asecond mode, outputting of the image data including only some of theplurality of color components being performed per-field in the firstmode, and outputting of the image data including all of the plurality ofcolor components being performed per-field in the second mode; aselecting unit that is configured to select two or more, but not all, ofthe plurality of fields, from among the plurality of fields, so tocontain all of the plurality of color components when theimage-capturing unit is switched to the first mode, and is configured toselect one field from among the plurality of fields when theimage-capturing unit is switched to the second mode; an image-generatingunit that is configured to generate a low-resolution image based onimage data of a field being selected by the selecting unit; and acontrolling unit that is configured to cause the image-generating unitto generate the low-resolution image.
 2. The image capturing apparatusaccording to claim 1, wherein the image-capturing unit is configured togenerate a thumbnail image that is different from the low-resolutionimage, by applying a resolution conversion to the low-resolution image.3. The image capturing apparatus according to claim 2, wherein thelow-resolution image is an image to be displayed on a display apparatus.4. The image capturing apparatus according to claim 2, wherein the imagegenerating unit is configured to generate a main image that is differentfrom the low-resolution image and the thumbnail image based on the imagedata separated into the plurality of fields and output by theimage-capturing unit.
 5. The image capturing apparatus according toclaim 4, further comprising: a record-controlling unit that isconfigured to record an image file into a recording medium, the imagefile including at least the thumbnail image and the main image.
 6. Theimage capturing apparatus according to claim 1, wherein in the firstmode, the image data having the plurality of color components isseparated into at least four even-numbered fields and each of the fieldsis output.
 7. The image capturing apparatus according to claim 1,wherein a color filter in a Bayer arrangement is disposed in theimage-capturing unit.
 8. The image capturing apparatus according toclaim 1, wherein the selecting unit selects, from among the plurality offields, a smallest number of fields necessary to contain all of theplurality of color components when the image-capturing unit is switchedto the first mode.
 9. The image capturing apparatus according to claim1, wherein: when the image-capturing unit is switched to the first mode,the controlling unit controls the image data of the field selected bythe selecting unit to be stored in a buffer and controls theimage-generating unit to read the image data stored in the buffer whilethe image-capturing unit outputs a field other than the field selectedby the selecting unit, and when the image-capturing unit is switched tothe second mode, the controlling unit controls the image data of thefield selected by the selecting unit to be transmitted to theimage-generating unit directly.
 10. The image capturing apparatusaccording to claim 9, wherein: when the image-capturing unit is switchedto the second mode, the controlling unit controls the image-generatingunit to generate the low-resolution image while the image-capturing unitoutputs the field selected by the selecting unit.